Polymers and production thereof



March 4, 1958 J. P. HOGAN V.ET AL v 2,825,721

PoLYMERs AND PRODUCTION THEREOF `Filed March 2e, 195e Sheets-sheet 1FVG.

Amze 25 N21 M i'ce AccuM'uLA-roR sx-:Ploru "'Ca/ |65/l JI4 f POLYMERINVENTORS JP. HOGAN RJ.. BANKS BY MKM A T TORNEVS March 4, 1958 ,1. P.HOGAN ET AL 2,825,721

POLYMERS AND PRODUCTION THEREOF Filed March 26, 1956 6 Sheets-Sheet 2INVENTORS J. P. HOGAN R.L. BANKS BY ATTO;

6 Sheets-Sheet 3 R.L. BANKS A TTORNEYS J. F. HOGAN ET AL POLYMERS ANDPRODUCTION THEREOF March 4, 1958 Filed March 26, 1956 M gk March 4, 1958J. P. HOGAN ET A1. 2,825,721

POLYMERS AND PRODUCTION THEREOF' Filed March 2e, 195e e sheets-sheet 4TI nO mmIUZ .mDmwm-mm mPDJOmm INVENTORS J.P. HOGAN R.L. BANKS BYATTORNEYS March 4, 1958 J. P. HOGAN I-:T AI. 2,825,721

` POLYMERS AND PRODUCTION THEREOF YFiled March 2e, 195e e sheets-sheet 5o e I6 24 32 4o 4s l ABSOLUTE PREssURE,INcI-IES OI= Hq THERMALDEPOLYMERIZATION (ISOTHERMAL) CURVES FOR POLYPROPYLENE ANDPOLYISOBUTYLENE PRESSURE vs TIME Lx. Oao ciu F/G. 6' 3 In? 5%6 IOo 4 eII2 IIe I2O 1- I-IExENE-I POLYMER PRODUCED AT I7o F JI- POLYISOBUTYLENE(COMMERCIAL) INVENTORS III- I-IExENE-I POLYMER PRODUCED AT2I5 F E SOSASN-X--EXPERlMENTAL POINT FOR II VARIATION lNwvlloIITY AT 2IoI= BY A TTURA/EVS March' 4, 1958 J. P. HOGAN ETAL 2,825,721

PoLYMERs AND PRoDUcToN THEREOF 6 Sheets-Sheet 6 Filed March 26, 1956INVENTORS J.P. HOGAN' R.L. BANKS ATTORNEYS N O O 7 Y IO l IN MICRONSWAVE NUMBER cm" s wml-:LENGTH B C K D nited States Patent ,szsf/zirom/'Mans man rnooocraon rnnnaon .lohn Paul Hogan and Robert L. Banks,Bartlesviile, irla.,

assgnors to Phillips Petroleum Company, a corporation oi Delaware.application Maren ze, 195e, senat mi. 573er/ 44 ciaims. (ci. 26o-sai)This invention relates to the polymerization of olelins. In one aspect,it relates to a novel polymerization catalyst and a method ofmanufacturing the catalyst. In another aspect, it relates to uniquepolymers.

This application is a continuation-impart of our copending applicationsSerial No. 333,576, led January 27, i953, and Serial No. 476,306, filedDecember 20, i954, both of said applications now abandoned.

lt is known that propylene and other low-boiling monoalkylethylenes canbe polymerized in the presence of metal halide catalysts to producepolymer products of dierent viscosities within the lubricating oilrange. Polymer products having improved viscosity characteristics havealso been obtained by polymerizing monoalkylethylenes in the presence ofdissolved aluminum bromide catalyst and catalyst promoter, such ashydrogen bromide, under conditions conducive to maximum growth ofpolymer chains. By this process, propylene polymer products in 100percent yield, having a viscosity at 210 F. of 15,000 S. U. S., orhigher viscosities which cannot be measured, have been obtained. Moreparticularly, the desired polymer products are obtained by admixingmonoalkylethylenes and aluminum bromide solution in the presence ofhydrogen bromide to produce a polymerization reaction mixture as a rststep, and thereafter, as a second step, adding monoalkylethylene slowlyto the polymerization reaction mixture. The two-step process producedpolymer products of higher viscosity than were obtainable by processespreviously employed. Prior to this invention, the polymerization ofolens to tacky and solid polymers had not been catalyzed by a highlyoxidized metal oxide as the essential catalyst ingredient, even thoughmetal oxide catalysts had been used in catalyzing the polymerization ofolefins to liquid polymers, such as propylene dimer and tetramer.

The objects of the invention are several:

To provide a process for polymerizing oleins in contact with novelcatalysts;

To provide novel solid polymers;

To provide a process for polymerizing l-olelins having a maximum of 8carbon atoms and no branching nearer the double bond than the 4-positionto tacky, semi-solid, and solid polymer;

To provide novel polymers of highl molecular weight from l-olens of thecharacter described;

To provide novel catalysts for olein polymerization;

To provide a novel method of preparing such catalysts which areparticularly active in polymerizing l-oleiins of the character describedto tacky, semi-solid, and solid polymer; and

To produce high molecular weight polymers which are improved VIimprovers from certain l-olens.

Other objects of the invention will become apparent from a considerationof this disclosure.

In accordance with this invention, polymers, including novel tackypolymeric products and/or solid polymers, are obtained by polymerizingpolymerizable olenic compounds in the presence of chromium oxideassociated with at least one oxide selected from the group consisting ofsilica, alumina, zirconia, and thoria. Solid polymers can be producedfrom monoolens and from diolens. Chromium oxide is an essentialcatalytic ingredient for the production of high molecular weight tackyand/or solid polymers according to this invention. This catalystcomprising chromium oxide is highly active in polymerizing certain olensto these heavy polymers. However, its capacity to polymerize oleiins tomaximum yields of tacky and/ or solid polymers appears to be highest inconnection with l-olens having a maximum of 8 carbon atoms and nobranching nearer the double bond than the 4- position. 1t doespolymerize olelns other than those mentioned, but the polymers arepreponderantly normally liquid. While the ensuing description dealsprincipally with liquid-phase operation, vapor-phase operation, withouta diluent, or with a diluent in liquid phase (so-called mixed-phaseoperation), is eiective in producing tacky and/or solid polymer.

Dioleiins, e. g., butadiene and isoprene, are among the l-oleiinspolymerized to solid polymers over our chromium oxide catalyst. ln thecase of conjugated diolens, a methyl group can be closer to a doublebond than the 4-position, The diolen must have at least one terminaldouble bond. Conjugated dioletins can have small substituents, e. g.,CH3, C2H5, as close as the 3-position to the terminal double bond.Noneonjugated dioleins exhibit the same characteristics as l-olens inour process.

The unique polymers according to this invention are characterized by thefact that their unsaturation is preponderantly of the trans-internal orterminal vinyl type. Certain of them are characterized in that theirunsaturation is almost entirely of the terminal vinyl structure.

Throughout the specitcation, it is to be understood that the term totalpolymer as applied to polymers of propylene, designates all polymerboiling above the monomer (but not including any diluent, of course);the semi-solid polymer constitutes the mixture or residuum remainingafter distilling off, or otherwise removing, the light oil boiling belowabout 900 F.; the tacky polymer is the lower molecular Weight portion ofthe semi-solid polymer, which portion can be extracted therefrom withn-pentane at room temperature; and the solid polymer is the highermolecular weight portion of the semi-solid fraction, which constitutesthe ranate or insoluble portion left from the extraction with n-pentaneor methylisobutylketone (MBK). Ethylene polymers according to thisinvention are composed preponderantly of normally solid material; onlysmall amounts of tacky or liquid polymer are ordinarily produced fromethylene. Polymers of l-butene, of l-pentene, and of 4-methyl-l-penteneaccording to this invention are similar to those of propylene. lt willbe readily understood by those skilled in the art, however, that themolecular weight distribution in any given polymer will depend upon, notonly the polymerization conditions, but the nature of the monomeremployed. Thus l-hexene, Lheptene and l-octene ordinarily giverelatively low yields of normally solid polymer and relatively highyields of serni-solid, highly viscous, or tacky polymer. However,4-rnethyl-l-pentene produces higher yields of solid polymer than doesl-hexene or l-pentene.

r,The polymerization of propylene over the catalyst according to thisinvention yields a total polymer product of about 2000 to 50,000 averagemolecular Weight. The molecular weight of narrow fractions of thepolypropylene produced by the process or" this invention in the presenceof chromium oxide supported on silica, alumina, or silica-alumina rangefrom about 200 to 100,000 or higher. Our polypropylene ordinarilycontains about l0 to 20 weight percent of material boiling below 900 F.ri`his fraction is an oil having an initial boiling point of about 400F. The fraction boiling above 900 F. coptaius both tacky and solidpolymer.

The tacky polymer product is useful in the manufacturing of surgical andpressure sensitive tapes, calking and sealing compounds, laminatedpaper, hydraulic fluids, tracing peper, electrical capacitors, surfacecoatings, rubber extenders, etc. Certain fractions of the polymerproducts are particularly useful as lubricating oil and as VII improversand blending materials for lubricating oils. The, solid polymers andcopolymers of the invention have utility in applications Where solidplastics are used. They can be coated on wire to provide insulation. They can be extruded to form filaments. They can be molded to formarticles of any desired shape, for example, bottles and other containersfor liquids. They are particularly desirable in these applications onaccount of their relatively high softening points which make themamenable to sterilization with superheated steam without deformation.They can also be formed into pipe or tubing by extrusion.

The catalyst according to this invention can be prepared by preparationmethods known iu the art, e. g. direct mixing of solid components,impregnation, etc. In order to obtain optimum activity, it is preferredthat the `catalyst mixture comprising chromium oxide and the additionaloxide as hereinbefore specified be heated under elevated temperature andfor a sulicient time to activate, or increase the activity of, saidcatalyst for the polymerization reaction. It is also preferred that thecatalyst be heated under nonreducing conditions in an atmosphere such asoxygen, air, nitrogen, carbon dioxide, helium, argon, krypton, or xenon.Reducing gases such as hydrogen or carbon monoxide can be present insaid atmosphere where the time of contact with the catalyst, especiallyat the higher temperatures, is limited to prevent extensive reduction ofthe hexavalent chromium; however, the pres-v ence of such gases, and ofreducing agents in general, is ordinarily not desired. It is ordinarilypreferred that the activation atmosphere be noureducing. It is furtherpreferred that the atmosphere be positively oxidixing, e. g. air oroxygen. The temperature and time of activation can vary over Wide rangesand are closely interrelated (so-called time-temperature etfect), longertimes being required at lower temperatures and shorter times at highertemperatures. Catalysts prepared by milling solid silica, alumina,zirconia and/or thoria with solid oxide are activatable at lowertemperatures than are catalysts prepared by impregnating silica,alumina, zirconia and/or thoria with an aqueous solution of a chromiumcompound. As a practical matter, a catalyst prepared by dry mixing isordinarily activated at a temperature of at least about 0 F.' and notsubstantially greater than about 1500n P. A catalystprepared byimpregnation with an aqueous solution is ordinarily activated at atemperature of at least about'450 F. and not substantially greater than15C0 F. Times of activation can range from about a second at the highesttemperatures to hours or more at the lowest temperatures. The statednumerical values are given as illustrative of the most practical rangesand are not absoylute limits. By using very short times and highertemperatures, or very long times and lower temperatures, catalystshaving various degrees of increased activation are obtainable.

The chromium oxide catalyst can be prepared by impregnation ofparticulate silica, alumina, or silica-alumina, for example, with asolution of chromium oxide or a compound convertible to chromium oxideby calcination, followed by drying and activation of the composite at atemperature in the range of 450 to 1500 F., preferably 750l to 1500 F.,for a period of 3 to 10 hours or more. Activation is conducted byheating in a stream of gas. It` is preferred that the gas contain oxygenand be substantially Water-free. Preferably the dew point` of theactivation gas shouldbe below 75 F., preferably below 0*. F. However,inert gases, such as carbon dioxide and nitrogen, can be used. It isfound thatwithin this activation range. of temperature treatment of thecatalyst, the

character of the polymer can be controlled. When the catalyst isactivated at temperatures in the upper part of the range, particularlyfrom 1300 to 1500 F., the polymers obtained from propylene and heavieroleiins have a lower average molecular weight and contain less tacky andsolid polymer, while activation temperatures in the lower part of therange produce a` catalyst which eiects an increase in molecular weightof the polymer and the production of larger proportions of heavy tackyand solid polymer. The catalyst can be prepared using, as startingmaterial, chromium trioxide, chromic nitrate, chromic acetate, chromicchloride, chromic sulfate, ammonium chromate, ammonium dichromate, orother soluble salts of chromium. The highest conversions were obtainedfrom the catalyst that contained only chromiumroxides after activation.Impregnation with chromium trioxide (CrO3) is preferred, althoughchromic nitrate can be used with similar results. It is believed thatthe catalyst prepared from the chloride and that prepared from thesulfate are at least partially converted' to oxide duringY activation.The amount of chromium, as chromium oxide, in the catalyst can rangefrom 0.1 to l0 or more weight percent and is ordinarily a minorcomponent of the catalyst in terms of weight percent. Chromium contentsas 'high as 50 weight percent are operative, but amounts above 10 weightpercent appear to have little added advantage for the polymerization ofethylene. However, for the polymerization of propylene and higherboiling olelins, chromium contents as high as 25 or 30 percent are oftenadvantageous. A preferred non-chromium component or support is asilica-alumina composite containing a major proportion of silica and aminor proportion of alumina. While the method of preparing thesilica-alumina composite undoubtedly aiects the catalyst activity tosome extent, it appears that silica-alumina composites prepared by anyof the prior art processes for preparing such catalytically activecomposites are operative for the process of this invention.Coprecipitation and impregnation are examples of such processes. Onesupport that has been foundparticularly eiective is a coprecipitatedpercent silica-l0 percent alumina support. It is found that steamtreatment of certain commercially available forms of silica-alumina orsilica Without appreciable alumina, improves the activity and life ofthe catalyst composite in a polymerization reaction. A silica support oflower surface area and larger porev sizel is a better support than onehaving extremely high surface area andv small pore size. These factorsare believed to bel of importance in the removal of the heavy polymerfrom the surface of the catalyst composite. A chromium oxide-aluminacatalyst ordinarily has aboutvtwo-thirds the activity of a chromiumoxide-silica-alumina catalyst. It is necessary for some of the chromiumto be in the; hexavalent state to act as an active promoter or catalystfor the polymerization reaction of this invention. It is preferred touse catalyst in which the amount of hexavalent chromium is atleast 0.1percent of the weight ofthe catalyst composite, at least at the initialcontactingl with the hydrocarbon; The hexavalent chromium is determinedby ascertaining the watersoluble chromium present by leaching with waterand determining'thedissolved'chromium in the leachings by any suitableanalyticalmethod known in the art,.e. g. addition of potassium iodidesolution and'titration of the liberated iodine with sodium thiosulfatesolution.

The preferred steam activation of certain silica-alumina bases,previously mentioned, is conductedat a temperature of approximately1200"F. for 10houi's utilizing l5 volume percent steam adrnixed withvolume. percent air. In the steamV activation treatment,- thetempera-ture can be varied'from- 1100-to 1300"' F. andthe steam contentof the steam-air mixture can rangerfrom about 3" to about 10 percent.The time of treatment canvary from about 4 to about 15 hours.

Another. suitable base. or support for our'L catalyst:

asomar 5 is microspherical silica-alumina containing, for example, l tol5 weight percent alumina.

The molecular weight of the product ycan be changed by pretreating thecatalyst base, preferably before addition of the chromium oxide, with afluoride, alone or in aqueous or non-aqueous solution, e. g., aqueous oranhydrous hydrogen lluoride or other organic or inorganic fluoride,especially a volatile fluoride such as ammonium iiuoride or ammoniumhydrogen fluoride, and heating, e. g., at from 300 to ll00 F. for from0.5 to l0 hours, to remove residual iiuoride. This treatment results ina catalyst which, after addition of the chromium oxide, produces apolymer of increased molecular weight and iiexibility. From 0.001 to 0.2part by weight of the tiuoride per part by weight of oxide treatedproduces the improved results, although these ligures do not representabsolute limits.

The terms support or base, as used herein, are not to be narrowlyinterpreted. They are not limited to mere inert components of thecatalyst mass. In fact, the nonchromium components appear to impart tothe catalyst at least part of its activity, and variations in theiridentity and proportions aiect the catalyst activity. The support ispreferably utilized in the porous form, e. g., a gel.

Other methods of preparing the catalyst, e. g., coprecipitation, arewithin the scope of the invention.

The temperature to be used in carrying out the polymerization reactioncan vary over a broad range but normally ranges from about l00 to about500 F., preferably l() to 450 F. The preferred range for propylene andhigher olens is 150 to 250 P., and that for ethylene is 275 to 375 F.when a lixed bed of catalyst is utilized. When a mobile catalyst isused, the preferred polymerization temperature range is 175 to 350 F.for ethylene and that for propylene and heavier olens is about 180 to200 F. At temperatures lower than those in the preferred ranges, therate of catalyst deactivation increases and catalyst-bed plugging mayoccur, and at temperatures higher than those in the preferred ranges,the rate of catalyst deactivation increases and polymer molecular weightdecreases. Our polymerization process is a relatively low-temperatureprocess. The maximum temperature of polymerization appears to be that atwhich reaction, other than polymerization, between the hydrocarbon feed,or some component or components thereof, and the catalyst proceeds atsuch a rate, relative to that of polymerization, that polymerization isnegligible, at least as regards the formation of solid polymer. Thistemperature is in the vicinity of 500 F. Grdinarily, the process isconducted at temperatures up to only about 450 F., and usually not above375 F.

The pressure is preferably high enough to maintain any diluent(substantially discussed) in the liquid phase and to assure that olelinsnot liquelied under these conditions are dissolved in the liquid phasein sufficient amount. This often, but not invariably, requires apressure of at least 100 to 300 p. s. i., depending on the feed and thetemperature, and a pressure of approximately 500 p. s. i. is to bepreferred. The perssure can be as high as 700 p. s. i. or higher, ifdesired. It can be as low as atmospheric when, for example, the reactionis conducted in the gaseous phase. As a general rule, high pressuresfavor the production of high molecular Weight polymers, all otherconditions being constant. rEhe feed rate can range from 0.1 to 20liquid hourly space velocity with a preferred range of l to 6 liquidhourly space velocity in a liquid-phase process with xed-bed catalyst.Hydrocarbon diluents, preferably parains and/or cycloparains, serve assolvents for the polymer products to aid in the removal of the productfrom the catalyst in the reactor or as diluents. The diluents includealiphatic paraiiins having from 3 to l2, preferably 5 to l2, carbonatoms per molecule. Any hydrocarbon diluent which is relatively inert,non-deleterious, and liquid under the reaction conditions of the processcan be utilized. Diluents that have been used successfully for thepolymerization of ethylene, propylene and other olens according to thisinvention include propane, isooutane, normal butano, normal pentane,isopentane, isooctane (2,2,4-trimethylpentane), cyclohexane, andmethylcyclohexane. hexane, the isohexanes such as neohexane anddiisopropyl, normal heptane, the isoheptanes such as 2-methylhexane andtriptane, normal octane, normal nonane, the isononanes, cyclopentane,methylcyclopentane, the dimethylcyclopentanes, and thedimethylcyclohexanes can also be used. Methane and/or ethaue can beused, especially Where gas-phase contacting is practiced, and forliquidphase contacting they can be used in admixture with the heavierhydrocarbons mentioned. The heavier paratdnic diluents have a highersolvent power for the product polymer than do the lighter ones. However,the lighter paraliins are quite useful in our process. Aromatichydrocarbon diluents are operative, although less preferred in manycases, since it appears that they require more expensive purication thando nonaromatics.

The polymerization can be eiected with a iixed-bed catalyst or with amobile catalyst. A frequently preferred method of conducting thepolymerization reaction comprises contacting the feed oleiin with aslurry of the comminuted chromium oxide catalyst in suspension in thesolvent or diluent. From about 0.01 to 10 weight percent of catalyst,based on weight of diluent, is ordinarily used. The catalyst can bemaintained in suspension by a mechanical agitation device and/ or byvirtue of the velocity of the incoming feed or diluent. In this type ofoperation, a large portion of the product polymer remains associatedwith the catalyst, which is withdrawn "rom the reaction zone, as aslurry. The polymer can be separated from the catalyst by dissolution ina solvent of the type described, usually with the aid of heat andagitation, and the stripped catalyst can be recycled and/or regenerated.The regeneration can be accomplished by oxidizing the residualcarbonaceous deposit with a controlled concentration of oxygen in aninert gas by conventional procedures. However the productivity of ourcatalyst is sufficiently high that it is often economical to discard theused catalyst after a single pass through the reactor. In some cases,especially where a pigment such as carbon black is to be added to thepolymer product, or where high polymer productivity is obtained, thecatalyst need not even be separated from the polymer.

One problem encountered in xed-bed operation of the polymerizationprocess of the invention lies in the plugging of the catalyst with heavypolymer. Periodically reversing the direction of ow of feed through thecatalyst bed aids in distributing the heavy polymer over the catalystand extends the time in which the catalyst can be utilized beforeregeneration is required. Etfecting the process by countercurrentlycontacting a slowly gravitating bed of the catalyst with the liquid feedmakes it possible to utilize the catalyst over longer periods of timebefore regeneration is necessary and entirely prevents plugging of thecatalyst bed which eventually occurs in fixed-bed operation. Theolen-containing feed, together with a hydrocarbon solvent, such asn-pentane or isooctane, under suticient pressure to maintain liquidphase, is charged into the bottom of the reactor and moved upwardly at alinear velocity which can be sumcient to give some expansion of the bedto prevent plugging by high polymer accumulation but insucient to causesubstantial top-to-bot-tom mixing of the catalyst. In this type ofoperation, it is possible to maintain a top bed temperature in the rangeof to 150 F. and a bottom bed temperature in the same range, while thetemperature of the middle section of the bed is maintained in the rangeof about 200 to 250 F. in propylene or higher 1-olen polymerization.This type of operation and temperature control elects the production ofa larger proportion of high molecular weight polymer in both the top andbottom sections NormalV t of the v:bed .and increases -fthe yield .oftack-y and solid polymer. Temperature :is controlled by regulating thetemperature ofthe feed and the temperature lof the incoming catalyst.The feed cools 'the hotter catalyst coming Yfrom the middle orintermediate section of the bed, and the cooler catalyst admitted to thetop section of the bed cools the .liquid passing into Ithe top sectionof the bed from the hotter intermediate section. In the moving-bedprocess, the liquid feed rate is maintained in the range of 2 to 6v./v./hr., the olelinconcentration, in the hydrocarbon feed, in ytherange of 0.1 to 25 weight percent, and the catalyst rate lin therange of0.1 to 0.5 v./v./hr. In this process, fresh olefin-containing feedcontacts the .less active catalyst at a minimum temperatureso thatexcessive reaction is avoided and heavier polymer is produced. Theupflowing feed vis heated by direct heat exchange with hot catalyst fromthe higher temperature region produced by heat of reaction, and thetemperature reaches a maximum ator'near the middle of the bed. As thefeed moves on up through the top part of the bed, it becomes moredepleted in o'le'iius and is cooled by direct heat exchange with coolerfresh catalyst. In the top part of the bed, the fresh, highly activecatalyst contacts the olefin-depleted feed at-ornear the minimumtemperature of the range so that excessive reaction is avoided andheavier polymer is produced. The euent from the top of the reactorcontains the total polymer' (except polymer deposited on the catalyst),together with the hydrocarbon solvent, such as pentane -or isooctane.Polymer remaining on the catalyst can be recovered, at least in part, bytreatment of the catalyst with a suitable solvent, such as thosepreviously described herein, at a temperature -above reactiontemperature, or by stripping thecatalyst with an inert gas at a stillhigher temperature, e. g., 700 to as high fas 1l00 F. or higher, the`effluent stripping gas being cooled to condense polymer removedtherein. The polymer can be recovered from solution in the solvent byevaporation of the solvent. Operation with the temperature gradientsindicated resultsfin considerable reaction at lower temperatures thanwould otherwise be possible, and ultimately results in the production ofheavier polymer. In addition, excessive reaction in a narrow zone Withplugging difficulties and catalyst .disintegration are avoided.

Used catalyst can be Vregenerated in auxiliary equipment in the usualmanner. The catalyst is'rst Washed with a hydrocarbon solvent, such aspentane, isooctane, or cyclohexane, at a temperature in the range ofy300 to 400 F. under Vsuicient pressure to maintainthe solvent in theliquid phase. Following this, solvent'vapor is removed by flushing withinert gas and any remaimngsolid polymer is removed from the catalystwith dry arr d1- luted with inert gas. The temperature at whichthe,sol1dpolymer is burned olf the catalyst is maintained preferably in the rangeof 900 to l100 F. Solid polymer 1s recovered from the solvent used inthe washingstep and the polymer-free solvent is reusable in subsequentwash ings.

In the drawings,

Figure l is a diagrammatic flow sheet of aprocess for conducting thepolymerization according to thtsinvention in a iixed-bed reactor.

Figure 2 illustrates another embodiment of the Invention in which asuspended catalyst is used.

Figure' 3 is a self-explanatory ow sheet illustrating the practice vofthis invention in connection with another type of polymerization processin which liquid polymers are the principal products.

Figures 4 and 5 are thermal depolymerization curves obtained withpolymers yof this invention and polymers produced according to the priorart.

vFigure 6 illustrates the relationship between viscosity index .andviscosity at 210 F..for alubricatingoilontainingpolymersprepared:accordingtothis invention-and rfor the .same .oil .containing .polymers prepared :according to theprior art.

Figure 7 shows infra-red absorption spectra of `three polymers accordingto this invention in `comparison with corresponding spectra oftwo otherpolymers.

As shown :in Figure 1, isooctane andethyleneare supplied through lines 2and 17, respectively,fto branch line 3 and reactor 6. vReactor 6contains a xed bed of compcsite chromium oxide catalyst of the typepreviously discussed and is connected in parallel with reactors 7 and 8,which also contain composite chromium oxide polymerization catalystaccording to this invention. The mixture of ethylene and isooctanevpasses through reactor 6 under polymerization conditions vpreviouslydescribed, for example, 330" F., 600 p. s. i. and a liquid hourly spacevelocity of 2. Theefduent passes through lines 9 and 10 to accumulator12. Fluid is withdrawn from accumulator i2 and passed through line 13 toseparation zone 14 wherein the efiluent is 'separated into two or morefractions, for example, van isooctane fraction, which is recycledVthrough conduit 16, and a product polymer fraction which is withdrawnthrough outlet 15.

After some time on stream, the activity of the catalyst in reactor 6declines as a result of the deposition of heavy polymer thereon. At thistime, the isooctane-ethylene feed is passed through branch line 4 intoreactor 7, and the reaction is conducted as previously described.Isooctane is supplied through line 18, heated, for example, to atemperature of 350 to 375 F. in heater 19 and is passed through lines 20rand 3 intoreactor 6, therein dissolving depositedheavy polymer. Theresulting solution can be passed through lines 9 and 10 to accumulator12, the polymer being recovered along with the polymer. obtained in thereaction etlluent, as previously described. Alternatively, part or allof the ysolution can be passed through lines 9, 22 and 24 andfractionated separately, for example, by fractional distillation. Thisprocedure is sometimes advantageous, since the polymer deposited on thecatalyst surface has a higher molecular weight than that obtained fromthe reaction eiuent and two diierent polymers can thus be obtained inthesame process. After the removal of deposited polymer from reactor 6 yhasbeen completed, the heated isooctane can be passed through lines 21 and4 to remove polymer deposited in reactor 7. The polymerization reactionis then conducted in reactor 8 by passing the isooctane-ethylene mixturethrough line 2, the eiiluent from reactor 8 being passed throughconduits 11 and 10 to separation zone 14, as previously described.Nitrogen, supplied through lines 25 and 27 to conduit 3 and reactor 6,is then used to ush hydrocarbon vapor-fromreactor 6 preparatory toregeneration. Air is then introduced into 'the system .through line 26and the catalyst is reactivated by combustion, as previously described,the combustion gas being Withdrawn through-outlet 29. By the use ofvalved conduits 28 and 25 and outlets 30 and 31, the catalyst masses inreactors 7 and 8 can likewise be regenerated. Thus, one of the reactorsis utilized for polymerization, while a Second is being operated toremove deposited polymer from the catalyst andthe catalyst in a third isbeing regenerated.

After regeneration, the catalyst is cooled in dry air or dry inert gas.If desired, a fourthl reactor (not shown) -can be utilized in parallelwith reactors 6, .7 and 8, so that regeneration of one mass of catalystby burning carbonaceous deposits therefrom and activation of ano-ther byheating ata high temperature, as previously described, preferably in thepresence of dry air, can be conducted simultaneously with polymerizationand polymer deposit removal.

In the system illustrated in Figure 2,- isooctane-enters through inlet40 and is mixed with comminuted chromium oxide catalyst supplied from.storage vessel 41 through conduit 42. The suspension of. catalyst insolvent passes to reactor 43,:which is maintainedunderfturbulencefeffective tofmaintainthe catalystimsuspension inthereaction mixture. In Figure 2, the turbulence producing means isillustrated as motor-driven stirrer 43A. However, other known agitationmeans, :auch as a jet agitator, can be used. Ethylene enters the systemthrough inlet 44 and is polymerized in reactor 43 under conditionspreviously described, e. g., 250 F. and 500 p. s. i. The catalyst supplyrate can be varied over a broad range, depending on the characteristicsof the particular catalyst used and on the reaction conditions. From0.01 to l parts by weight of catalyst per 100 parts by Weight of solventgive satisfactory results in most cases. An eiiuent in the form of aslurry is removed from the reactor through line 45 and passed togas-liquid separator 46 wherein unreacted ethylene and/or other gas isseparated from the liquid and solid phases and is recycled throughconduit 47 and compressor 48. Part or all of this gas can be removedfrom the system through means not shown. Such withdrawal is oftendesirable when substantial amounts of inert gas are present in the gasfrom separator 46. The nongaseous material is passed from gas-liquidseparator 46 through conduit 49 to solution zone Si? which is providedwith stirrer 50A and heating means, such as a steam coil 50B. Insolution zone 50, the mixture is heated to a temperature at least 25 F.above the reaction temperature and is subjected to agitation for asucient time to effect solution of the polymer in the solvent, exempliedhere as isooctane, which is maintained in the liquid phase byapplication of pressure. Additional solvent can be added through inlet51. A highly desirable method of effecting the dissolution of thepolymer is described in more detail in the copending application of I.P. Hogan and E. R. Francis, Serial No. 445,042, led July 22, 1954. Theresulting mixture of solution and catalyst is passed through conduit S2to solids separation zone 53, which can be a centrifuge, a iilter orother known equipment for the removal of solids from liquids at elevatedtemperatures and pressures. The catalyst is removed through outlet 54,and can be recycled, by means not shown, passed to a regenerationsystem, also not shown, or can be discarded. The regeneration can beeffected as previously described. lt will be evident to those skilled inthe art that known techniques of iiuidized catalyst regeneration can beapplied to the catalyst regeneration step hereinbefore described. Thesolid separation in zone 53 is conducted under substantially the sametemperature and pressure conditions as obtained in solution zone 50.Solid-free mixture passes through conduit 55 to fractionation zone 56,which can be a fractional distillation apparatus, evaporation equipment,or apparatus for chilling the solution, for example, to about70 F. orlower,

to precipitate the polymer as a solid and recover the precipitatedpolymer by ltration, for example. Recovered isooctane is recycledthrough conduit 57, and product polymer is recovered through outlet S.

Further, according to this invention, special benets can be obtained byutilizing, as feed to the process, a mixture of at least two differentoleiins. For example, ethylene and propylene can be copolymerized, ascan ethylene and l-butene, l-butene and propylene, or propylene and apentene, in the presence of a chromium oxide polymerization catalyst. Byusing a propoylene-ethylene mixture containing from to 45 Weight percentpropylene as a feed component, a copolymer is obtained which hasincreased exibility and is readily capable of being extruded to form afilm, Films of this type are unusually resistant to moisture-vaporpenetration and are useful as wrappings for foods, drugs, chemicals, andthe like. By using, as a feed ingredient, a propylene-ethylene mixturecontaining from 0.5 to l0 weight percent propylene, spalling ordisintegration of the catalyst particles is decreased. This is anadvantage in a lixed-bed or gravitating-bed process where filtration isnot needed for catalyst removal. A similar eiect is obtained by the useof a propylene-ethylene mixture containing from about 1 to 10 about 20Weight percent ethylene. The preferred ternperature range forethylene-propylene copolymerization is from 175 to 320 F., morepreferably 200 to 280 F.

Many of the copolymers of this invention have a ilexibility rating, asdetermined by the falling ball method, of at least 72 inches, even whenproduced in a xed-bed process. This rating is determined by allowing agram steel ball to fall from a measured height and strike a molded discof the copolymer two inches in diameter and one-eighth inch thick. Theball falls along a mechanical guide, and the height from which the balldrops is measured. The minimum height required to shatter the moldeddisc is taken as a rating of flexibility or susceptibility toshattering. The maximum height measurable according to this method andapparatus is 72 inches. Thus, many of the copolymers of this inventionare not shattered by the falling ball within the limits of measurementof the method. in contrast, so-called brittle polymers can be shatteredby the ball when it falls from a much smaller height, such as no morethan 6 to 10 inches.

In addition, diolefins can be copolymerized with 1- monooletins of theclass herein dened. Thus ethylene and 1,3-butadiene have beencopolymerized, according to this invention, in a 9:1 Weight ratio in thepresence of a chromium oXide-silica-alumina (2.5% Cr) catalyst at 270 F.to obtain a copolymer having a molecular Weight of 33,690.

The polymer and copolymer lms prepared according to this invention havea moisture penetration rating not greater than l gram per mil thicknessper square inches per 24 hours. The method of determination of moisturetransmission or penetration is referred to in certain of the subsequentexamples. The iilms are also characterized by having transverse tearstrengths of at least 170, and often at least 185, grams per mil ofthickness, as determined by a method subsequently described herein.

Films extruded from solid, flexible, high copolymers prepared by thecopolymerization of ethylene with propylene over a chromiumoxide-silica-alumina catalyst according to this invention have, inaddition to very low moisture-vapor permeability, good tensile strengthand tear strength. They are superior in moisture-vapor permeability tolms prepared from presently available commercial polyethylenes producedby other processes. They are particularly desirable for film packagingmaterials for meats, cheese, fresh vegetables, dried eggs, milk, etc.,and for coating paper to be used as packaging material. Films ranging inthickness from 1/8 inch to 0.001 inch or less can be prepared from thecopolymers of this invention.

Films prepared by blending commercial polyethylene with solid ethylenepolymers prepared over a chromium oxide-silica-alumina catalyst have lowmoisture-vapor permeability. Films prepared from ethylene-propylenecopolymers, as herein described, have properties as good or better thanthose prepared from blends of the two types of ethylene polymers and, inaddition, there are certain advantages in the process steps for theproduction of the copolymer films. Ethylene-propylene copolymers arereadily prepared and used as such for extrusion into iilms withoutfurther processing.

Many of the ethylene-propylene copolymers of this invention are flexiblematerials which generally have a melt index less than 25, preferablybetween 0.01 and 1.0. (Melt index, as determined by ASTM method D1238-52 T, is the rate of extrusion of a thermoplastic material throughan oriice of a specified length and diameter, under prescribedconditions of temperature and pressure.)

The following specific examples present data which illustrate andclarify the invention but should not be so interpreted as to restrict orlimit the invention unnecessarily.

1 l SPECIFIC EXAMPLES Example Irv-Polymerization of olefns over chromiumoxide-. silca-alumna- Individual monoolens and diolens were polymerizedin dow-type runs over a fixed bed of 3 percent chromium as oxide in a`chromium voxide-silica-alumina1 catalyst (prepared by impregnationwitht CrO3 solution, activation above 700 F. in dry air) at about 600pounds per square inch at a temperature of about `19,0" F. ,and a`liquid hourly space velocity of 2, the feed containing 20 mol percentreactant and 80 mol percent isobutane. Most runs were for .4 to 6 hours..The results of the conversions andthe qualitative nature of thepolymers are given in Table I.

l:TABLE I Average Monomer Conversion, Type of Polymer, etc.

Percent Normal 1olefins:

Ethylene 100 Solid, slightly waxy. AReactor plugged in 2 hrs. Propylene91 Tacky, semi-solid. 1-Butene- 77 Tacky, elastic semi-solid. l-Pentene82 Tackier than polypropylene;

semi-solid. 1-Hexene 40-56 Verilrldtacky, transparent semiso i 1-Octene58 Tacky, contained about 4-wt.% solids including wax (possibly dimer ortrimer). 1Dodeeene 16 (Run at 260 F.) liquid. Normal Z-olens:

Liquid (dimer and trimer) 5 Liquid (dimer and trimer) Y11 Liquid (dimerand trimer). Z-Octene 1 Wax (probably dimer and trirner). Branchedl-olens:

Isobutylene 87 Liquid (dimer and trimer). 2-Methyl-1-butene 6 Liquid(dimer and trimer). 3-Mcthyl-1-butene. 15 Liquid (dimer and trimer).4-Methyl-1-pentene .80 Semisolid. 4-Vinylcyclohexene 6 Liquid. Branched2-olelns:

2-methyl-2-butene. 12 Liquid. Cyclic Olens:

Cyclohexene 5 Liquid. Diolens:

Butadiene 55 Solid. Isoprene 34 Solid. Aryl Oletins:

Styrene 0 The results show that onlyl-olens give the high polymer.Normal l-olens give high polymers which vary in degree of solidity andtackiness as noted. Ethylene reacted most vigorously, and it appearedthat the reaction rate decreased as the length of the polymer chainincreased.

For the branched 1-olens tested, any branching closer to the double bondthan the 4-position prevented formation of heavy polymer.-4-methyl-1-pentene gave semisolid polymer which was successfullyexpelled from the reactor in continuous-ow operation. Y

Both 1,3-butadiene and isoprene gave solid polymer.

Example II.-Effect of temperature on propylefre conversion Runs weremade with chromium oXide-silica-alumina (Weight ratio SiO2:A12O3=9: 1)catalyst containing 3 percent chromium as chromium oxide (prepared asinExample l), operating at 600 pounds per square inch, a liquid hourlyspace velocity of 2, and a feed consisting of 1l moi percentpropylene,`l-4vmol percent propane, and

74` molpercentisopentane. lThe data obtained are given in v'Table Hfandirnlicatealiv Optimum temperature-,range of 150 to 250 F.

Propylene Conversion, Percent Temp., F After 2 hrs. 3 hrs. 4 hrs.

Example III Hydrocarbon diluent was varied in runs made at to F., 600pounds per square inch, two liquid hourly space velocity of feedcontaining propylene, propane and other diluent. The results are givenin Table III. An improvement in conversion wasvobtaineqd as the`molecular weight of the feed diluent was increased from propane toisobutane to pentane or isopentane. No further improvement was obtainedin short runs with isooctane as diluent. However, in longer runs,isooctane showed Virnprovement over` the other diluents, as shown inTable lV.

[Operation at 220 F., 600 p. s. i. g., 2 L. H. S. V. of feed,containingSmol percent 03H6, 12 mol percent 03H5, 79 molpercent-solvent.]'

Percent 03H8 Conversion, Hrs. Solvent Isopentane Isooctane The catalysthad the same composition las that in Example lI and was prepared in thesame manner, i. .e impregnation and activation as previously described.

Example I Tfr-Suspended catalyst Shaker-autoclave tests were made tostudy batch Voperation and to determine the effects of Varying thefeedto-catalyst ratio in this type of operation. The catalyst was14/28vmesh silica-alumina 1 promoted with 3 percent by Weight ofchromium as chromium oxide and Vactivated at 930 F. (preparation aspreviously described). The feed stock was a blend of 20 mol percenttechnical grade -propylene and 8O mol percent-technical grade isobutane.The catalyst was suspended in the liquid charge in the shaker-autoclavefor six `hours at-a temperature of 190 F. The results of these tests areshown in Table V. For a constant reaction time of 6 hours, the 4totalpropylene conversion decreased from 98 percent with a 4:1feed-to-catalyst weight ratio to 18 percent with a 50:1 ratio. However,calculations showed (see Table V) that the grams Aof propylene convertedper'grram 'of catalyst increased-from 0.54 with a 4:1 feed-tocatalystratio to,l.41 with a 10:1 ratio, and thereafterremained relativelyconstant.

1 S103 Aware :.1 by weight.

TABLE V Propylerze conversion per gram of catalyst n autoclave tests[Six-hour tests at 190 F. with 20 rpoldplercent CaH, 80 molpercentiC4H1o 5 Feed-to- Percent Grams CsHe Catalyst 3 e ConvertedWeight Converted Per Gram Ratio oi Catalyst Example V.-Chromium oxidecontent of the catalyst To determine the effect of chromium oxidecontent of the catalyst upon activity of the catalyst and nature of theproduct, catalysts were prepared by impregnating a commercial steam-agedsilica-alumina support with aqueous chromium nitrate or trioxidesolutions over a wide range of concentrations. The results of propylenepolymerization tests with these catalysts are shown in Table Vi. Thesupport contained 90 weight percent silica and l0 Weight percentalumina. The catalyst was activated by heating for several hou-rs at 900to l000 F. in anhydrous air.

TABLE 'VI Variation of chromium oxide content of catalyst y'Commercialsteam-aged silica-alumina, 14/28 mesh, promoted With various amounts ofchromium oxide. Runs made at 180 to l90 F., 600 p. s. i. g., and 2 L. H.S. V. of 12 mol percent propylene, 13 mol percent propane, 75 molpercent isopentane feed.

Chromium Content Percent CGH@ Conv.,Hrs.

of Catalyst, Wt.

Percent Nature of Polymer 83 94 88 Sirupy semi-solid. 87 94 97Semtsolid, tacky. 95 98 97 Semi-solid, tacky. 95 97 97 Semi-solid,tacky. 80 89 Semi-solid, tacky.

From the results shown in Table VI, it appears that the preferablechromium oxide content of the silicaalumina support was in the range ofone to three weight percent, expressed as chromium, under the conditionsinvestigated. The catalysts of higher chromium oxide content producedwhat appeared to be slightly more viscous polymer, but the effect wassmall considering the range covered.

TABLE VII Five-hour runs with ethylene were made at 308 to 313 F., 400p. s. i. g., 4.6 to 5.2 L. H. S. V. of about 3 weight percent ethylene,97 weight percent isooctane (2,2,4-

1d Example VI Table VIH presents the results obtained with supports ofvarying silica-alumina r; io and source, and from supports yother thansilica-alumina- Each catalyst was prepared by impregnating the 14/28mesh support with an 0.8 molar aqueous solution of chromium nitrate,drying, and activating for ve hours at 930 F. in dry air. The finishedcatalyst contained about 2 to 4 Weight percent chromium as oxide. Thecatalysts were then tested in polymerization runs withpropylene-propane-isopentane feed as described in Table VIII TABLE VIIISurvey of catalyst supports Chromium oxide-promoted catalysts Wereprepared from the supports shown. Polymerization tests at 180 F., 600 p.s. i. g., and 2 L. H. S. V. of l2 mol percent propylene, 13 mol percentpropane, 75 mol percent isopentane feed.

Percent 03H3 Conv.1

5% silica, 95% alumina gel Brucite (magnesium ox Activated carbon.. 86%SiOz-10% ZrO2-4% A Chrome-bead SiOz-AlzO; (0.4 wt. Cr).

1 High molecular' weight tacky and solid polymer was produced 1n allruns 1n which propylene was converted.

It is seen from T able VH1 that, although conversion of propylene wasobtained over the entire range of silicaalumina ratio, the catalysts ofhighest activity were prepared from coprecipitated 90 silica-l0 aluminasupports. The 54 silica-46 alumina support was an acid-activatedhalloysite clay.

The commercial pellets and commercial bead supports were of the sameapparent chemical composition (90 percent silica, l0 percent alumina),but the pelleted support, which was prepared by coprecipitation andsteam aging, appeared to provide a more satisfactory catalyst. Onaccount of the differences in methods of preparation of these twosupports, the commercial pellets have lower surface area and larger poresize than the beads and have a greater number of so-called macroporesper unit Weight lor Volume. These factors are believed to be ofimportance in the removal of the heavy polymer from the chromiumoxide-silica-alumina catalyst surface.

The HF-treated alumina in Table VH1 was prepared by precipitatingalumina gel from 3640 grams of aluminum nitrate nonahydrate in solutionin 28 liters of water by addition of 2 liters of 28 percent aqueousammonia, mixing the ltered, undried gel with 9.5 ml. of 47 percentaqueous hydrolluoric acid in 200 ml. of Water, stirring for 2 hours,drying the mixture at 215 F. for 24- hours, calcining at 750 to 800 F.for 20 hours, forming the solid into pellets by use of a hydrogenatedvegetable oil as a binder, and burning out the binder at about 1000 F.

The tWo supports containing neither silica nor alumina gave noconversion of propylene. A catalyst prepared with commercialsilica-Zirconia-alumina cracking catalyst as support gave goodconversion. The commercial chrome-bead silica-alumina cracking catalyst,already containing 0.5 percent chromium oxide, produced high molecularweight polymer from propylene with no further asamal Y1,5 addition ofchromium oxide but the activity declined relatively rapidly. I

Example VIL-Metal oxide components A survey of lthe available metaloxides as possible catalyst components Was made and the results of thesurvey are presented in Table IX. In each case, com- Percent CiH Conv.

Impregnatng Solution Probable Component Polymers Description 2 Hrs. 5Hrs.

Cr(NO5)a-9H2O CraOa-CrO: 82 86 Semisolid, taclry. CrOa CrzOa-CrOs 75 84Semisolid, tacky. CrCl3-6HgO- CrClz-(CrzOa-CIOQ). 66 49 Semisblld,tacky. Cr2(S Orla-5520 Cr2(SO4)aCrzOa-Cr0a.. B6 50 Sirupy, tacky.

E2C leductlon of CrOs 25 17 (4 hrs.) Liquid.

mercial coprecipitated steam-aged 90 silica-l0 alumina 20 TABLE IXSurvey of metal oxide promoters Commercial 90 silica-10 alumina, 14/28mesh, promoted with the compounds listed. yPolymerization tests at 160F., 600 p. s. i. g., and 2 L. H. S. V. of 25 percent propylene, 75percent propane feed, 5-hour runs.

As shown in Table YX, all of the catalysts prepared from the variouschromium compounds produced high molecular Weight polymer, but thehighest conversions were obtained from the catalysts that contained onlychromium oxides after activation, i. e., those prepared from chromiumnitrate and chroium trioxide. Whether the catalysts prepared from thechloride and sulfate produced high polymer only as a result of partialconversion of chloride or sulfate to oxides during activation is notknownbutseems likely.

Treatment of chromium oxide catalyst with hydrogen for four hours at 920F. to reduce hexavalent chromium to the trivalent state gave an catalystWhich was almost completely inactive for formation of high polymer. Thisindicates that hexavalent chromium is essential. Analyses Percent 03H5Probable Conv.

Impregnatlng solution Component 2 Hrs. 5 Hrs.

State N o Promoter 1 Times other than 5 hr. are shown in parentheses.

It is seen from Table lIX that only chromium oxide promoted theformation of high molecular weight polymer. A number of other metalcompounds acted as promoters yfor the formation of liquid polymer, ascaube seen by :comparing the conversion obtained in Veach run with thatobtained with the unpromoted ksilicaalumina base, shown :at the bottomyof the table.

Example KUL-Survey of chromium compounds as catalyst componentsCatalysts were prepared from various soluble chromium compounds byimpregnation of commercial steam-aged90 Asilica-1 0 alumina with anaqueous solution of the compound, followed by drying and activating at,79.30 in dry air. AEach catalystfwas` lthen tested in a propylenepolymerization run `as described in Table X.

have indicated that a major portion of the chromium oxide present on thecatalysts activated at930 F. in air was hexavalent. (Note Tables XI andXlI.)

Example IX .-Variatz'on of catalyst activation temperature The etects ofcatalyst activation temperature on cata-v lyst activity and ycharacterIof polymer were determined over a temperature range of TSO-to l500 F.The catalysts were tested in six-hour propylene polymerization runs atthe conditions desoribed' i111 ,T abl X- 'TABLE XI Catalyst, 14 to 28mesh commercial steam-aged 90 silica-l0 alumina impregnated withchromium oxide,

tested in six-hour polymerization lruns at 190 F., 600

asesinas 17 t p. s. i., and 2 L. H. S. V. of 12 mol percent propylene,

13 percent propane and 75 percent isopentane feed.

lDoes not include heavy material which remained on the unushed catalyst.

The data in columns 3, 4, and 5 present the weight percent of chromiumon the catalyst, the amount of hexavalent chromium, and the fraction ofthe chromium that is hexavalent. The amount of hexavalent chromium wasdetermined on the basis of water-soluble chromium.

The heavy ends were determined by ltering and Weighing the portion ofpolymers which were insoluble in methylisobutylketone (MIBK) at 200 F.and a solvent to polymer ratio of 40 ml. to one gram. The analysesreported in Tables YI and XII were on polymer samples collected in thesolvent-removal ash chamber during the run.

As shown in Table XI, the activity of the catalyst increased as thecatalyst activation temperature was increased -over the range of 750 to1500 F. The amount of heavy ends in the polymer, as indicated by theamount of MIBK insoluble at 200 F., was affected by the activationtemperature, and apparently the molecular weight of the polymerdecreased at the higher activation temperatures.

The ratio of hexavalent chromium to total chromium on the catalystdecreased as the activation temperature was increased.

Several catalysts were prepared by impregnation of commercialmicrospheroidal (99 wt. percent ner than 100 mesh) silica-alumina (about13.3 wt. percent alumina, remainder essentially silica) with an aqueoussolution of chromium trioxide. The catalysts were uidized in dry airduring activation. Polymerization tests were carried out in a batch-typestirred reactor at 450 p. s. i. g. and 270 F. using cyclohexane assolvent. Approximately 300 grams of solvent and from 0.45 to 1.0 gram ofcatalyst were charged to the reactor. After heating the reactor contentsto reaction temperature, the reactor was pressured with ethylene towithin 50 p. s. i., of operating pressure within the first live minutes,and, after the operating pressure of 450 p. s. i. g. was attained,ethylene was fed at the rate required to maintain that pressure. Theduration of each run was three hours. The results, which are presentedin Table XI-A, show that, as a practical matter, the minimum activationtemperature for the catalyst tested lies between 400 and 450 F. when thepolymerization is carried out under the conditions of these runs. If thedata for the activations at 450, 555, 650, 700, and 750 F. are plottedon rectangular nonlogarithmic coordinates and if more weight isarbitrarily assigned to the point at 650 F. than to that at 555 F., theminimum activation temperature appears to lie between 430 and 440 F. Theminimum activation temperature would be lower if relatively longactivation times were used. From a practical point of view, the minimumactivation temperature can be considered to be about 450 F. This minimumactivation temperature applies only to catalysts prepared by a wetmethod such as impregnation. This point is subsequently discussed inmore detail.

TABLE XI-A Activation temperature for catalyst prepared by impregnationCatalyst Activation Catalyst Testing Tempcr- Time, Percent PercentProductlv- Reaction ature, Hours Total Cr Cr+ ity #H Rate,

F. #/#IHL Several runs were carried out to determine the activationconditions for catalysts prepared by dry mixing of chromium trioxidewith the previously mentioned microspheroidal silica-alumina. Thesilica-alumina was calcined in air for ve hours at 1l75 F. Thecalcination was carried out with the material in the uidized state.After cooling to room temperature, grams of the silica-alumina was mixedwith 10 grams of dry chromium trioxide in a dry nitrogen atmosphere byshaking in a flask. Portions of this mixture were further treated asdescribed in Table XI-B, and the resulting catalysts were tested forpolymerization activity in a batch-type, stirred reactor at 450 p. s. i.g. and 270 F. About 300 grams of cyclohexane and 10 grams of catalystwere charged to the reactor, and, after heating the reactor contents toreaction temperature, the reactor was pressured to reaction pressurewith ethylene within live minutes. The run duration was two hours. Theresults which are presented in Table Xl-B, indicate that optimumactivity is obtained by heating. The loss-on-ignition data indicate thatmoisture was not excessive in any catalyst tested and, consequently,that it was not limiting.

TABLE XI-B Activation temperature for catalyst preparation by dry mlxllgCatalyst Preparation Catalyst Testing, Yield, Method of Mixing OrO;Percent Percent Percent #li with Silica-Alumina Total Cr* Loss onCatalyst Cr Ignition1 Fluidlzation2 at 80 F. for

two hours 2.5-3.0 2. 73 0.1 Fluidization at 400 F. [or

two hours 2. 5-3. 0 1. 56 3. 6 Ball-milled in Dry N 2 at 80 F. for 15hours 2. 5-3. 0 2. 64 2. 83 0.4 Ball-milled 15 hours, followed byfluidization at 400 F.

for two hours 2. 5-3. 0 2. 74 13. 8 Ball-milled 15 hours,s followed byuidization at 950 F. for five hours 2. 96 1. 49 1. 91 376 CalcnedSilica-Alumina with no Cro: 1.28 0.1 Ball-milled 15 hours, followed byfiuidization at 350 F.

for two hours 2. 96 4. 2

l l Heated at 1,760 F. in air for 16 hours. Figures not corrected forCrt s. 2 All iluidization was donc with dry air. 1 0.5 Gram catalystused in the polymerization test.

vthesurface of the silica-alumina.

content of the catalyst must be reduced to a certain level for thecatalyst to possessitstgrcatest activity. Apparently this level ofmoisture content is notreached in a reasonable time at temperatures muchbelow 450 F. On the other hand, when a dry method of preparation isused, for example, mixing of solid CrO3 with calcined silica-alum-ina,the moisture content need not be limiting, and the minimum temperatureappears to be that at which the C1'O3 has sufficient .mobilityto-.become distributed on For microspheroidal silica-alumina, this-minimum temperature appears to'bc a little below "350 F., although 350F. could beconsidered as a minimum froma practical point of View.

Example X Efect of aging offcatalyst with dry airand with wezz-ar Tostudy they effects of prolonged treatment of the catalyst vwith dry.airfand-with Wet-*air at elevated temperatures,suchaswould vbeencountered in repeated. regenerations, the catalysts were `agedS8-hours. at l 100 2F.land

.1300-F. with dry air andat llO0 F. withainsaturated with -water vaporyat 100 F. At the end of-the aging period with the wetair, whichcontained about 6.5 percent Waterfvapor.: the catalyst was swept withdry airfor tive yhours at l100 F. Results of the polymerization-testonthese catalysts and similar data on unaged catalysts are. show-n inTable XII.

TABLE XII .20 as otherwise described. .The data presented in the suc-`ceecling examples were obtained by'contacting the feed with %2 x lrya@in'chpellets of coprecipitated 90 silica-l0 alumina impregnated withchromium oxide (aqueous Cros), except where specicallyindicated'other-wise.

.Example vXl.-Catalyst Supports: Variation 'of silicaalumina. ratioCatalyst :supports .of 90-10, 50-;50, and 10`90 .silicaaluminacompositions Wereprepared by pilling-a mixture of silicic acid andprecipitated aluminaandcalciningat 1000" F. The catalyst bases were.impregnated with 0.8- ..molar..chromiumxtrioxide .solutioniand activatedat 1300" :F.in dry air. Results and operating conditions of thevpolymerization tests onthese catalysts along With-data ten catalystsprepared using commercial 'steam-agedQO silica-10 alumina base are shownin Table XIII.

TABLE XIII Chromium oxide-promoted catalyst, 5/2-inch pellets, wereprepared from the support shown. Polymerization tests at 220'-F.,l 600p. s. i: g. Aand 2 L. H. S. V. of 7"mol percent propylene,9"percent'propanc Aand 84 .percent isopentane lfeed.

Catalyst Support Polymerization Test, Percent Physical Propylene Conv.,Hrs. l Condition of Used Catalyst Percent Percent 2 i5 10 15 .SilicaAlumina 10 Q0 62 I .39 29 26 Good. 50 80 72 42 23 Good. 90 10 88 91 6517 Spallcd. 90 1 10 -94 95 92 84 Good.

1 Commercial, steam-aged.

Catalyst Treatment Catalyst Analysis Polymcri Polymer zntlon An:.lys1s,1Test, yMIB Total Cr+r Total Average Insoluble Temp. F. Gas Time, Hrs.Cr, Wt. Cr6 Wt. Cr Calls at 200 F.

Couv Wt Percent Percent Percent Percent 1100 Dry Ati- '5 2.1 1l9 0.9 984.4 1100 Dry A -88 2.1 1.9 0.9 599 2l2 1100 Wet A1r2.. `88 2.5 0.1 0.1.55 `5.1 1300 Dry Air... 5 2.2 1.6 0.7 98 22.4 1300 Dry Air B8 2 0 1. 10. 5 '98 2. 5

l Does not include heavy material which remained on the unushedcatalyst. 2 Wet air contained about' 6.5 percent water vapor. .Catalystwas .tushed withdry air for ve hours at 1,100 F. after the wet nirtreatment.

As shown in Table XII, treatment with drylair for 88 hours at 1l00 F.resulted in a catalyst which had slightly higher activity and produced alighter Weight'polymer than did the catalyst activated at l100F. for 5hours. Similar variation in the time of treatment at l300.kF. did notaffect the catalyst activity or polymer distribution. The ratio ofhexavalent to totalchromium on the catalyst was not affected at 1100 F.,but decreased slightly at l300 F. by the prolonged treatment.

Treatment with air containing about 6.5 weight percent water vapor for88 hoursat'llOO" F. .decreased the activity of the -catalystconsiderably and, as .comparedwith the run at 1l00 F. for SShours,doubled'the fraction of polymer insoluble in MIBK vat 200 F. Thiscatalyst, which contained less than 0.1 .percent hexavalent :chromium,was a bright-green color as .compared to a graygreenfor that treatedWith'dry'air at1l00 F.

. All .of the data presented in the previoussexampleswere obtained.using .14 to "2S-.imesh catalysttparticles, :except Example JUL-Effectsof variation of operating tempera ture Furtherstu'des-were made Aon theei'rects'of operating temperature, `and longer tests and more accurateevaluations ofthe polymer -wereobtained Results and'operating.conditions of these .testsr-are vshownin TableXIV.

The polymer analyses wereon samples which includedthe asomar polymerushed from the reactor at the end of the runs. Comparisons of polymerswere based on the quantity of light and heavy ends. The light ends weredetermined Example XIV Table XVI presents data obtained on polypropyleneas a VI improver.

by vacuum distillation and are reported as Weight percent TABLE XVIpolymer boiling ybelow 850 F. at one atmosphere pressure. 5 The heavyends were determined by filtering and weigh- Polypropylene ing theportion of polymers which were insoluble in methylisobutylketone (MIBK)at 200 F. and a solvent VI i- ZYIF l to polymer ratio of 40 ml. of onegram.

TABLE XIV Solvent Rened MldContlnent 2L H S V f7 1 ou 100 119.8 41.04Operation ait 6009p. s. i. g. and 821 o 1.110 game ajdddiit percentpropy ene, percent propane an percent isoamc u I a ive. pentane feedover chromium oxide-90 silica-l0 alumina Same On+137 additive 130 414'868's pelleted catalyst activated at 1300 F. in dry air. :s Ug

Pol erlzation Tests Polymer Anal sis ym y Physical Condition OperatingPercent Propy ene Conv., Hrs. MIBK of Used Temp., Wt. Percent insolubleCatalyst F. 850 F. at 200 F..

5 10 20 30 40 Wt. Percent 190 94 8s 45 20 8 10 10.2 Spaued 220 95 92 7252 44 16 7.3 Good. 245 91 79 2s 27 5.1 Good (20 hrs.). The maximumconversion and longest cycle length at Example XV high conversion wereobtained at 220 F. The molecular weight of the polymer decreased, asshown by the increase in 850 Ff polymer and decrease in MIBK insolublepolymer, as the temperature was increased from 190 to 245 F. About 25percent of the catalyst used in the run at 190 F. was spalled orcrumbled. Most of this catalyst disintegration occurred in the top(inlet) portion of the catalyst bed. The catalysts used in the runs atthe higher temperatures remained in good physical condition.

Although higher conversion was obtained and less physical damage to thecatalyst occurred at 220 F., polymer containing greater amounts of tackyand solid materials was produced at 190 F. operating temperature.

Example XUL-Eeels of variation of propylene concenlraton The eects ofpropylene concentration in the feed upon conversion, polymercomposition, and catalyst spalling Were studied with feeds containing 4,7, and 12.5 percent propylene. Results of these runs are shown in TableXV.

TABLE XV Operation at 220 F., 600 p. s. i. g., and 2 L. H. S. V. of feedcontaining propylene, propane and isopentane over pelleted steam-aged 90silica-l0 alumina-chromium oxide catalyst activated at 1300 F. in dryair.

Table XVII shows pentene polymer produced with chromiumoxide-silica-alumina catalyst is also a good VI improver.

Polyisobutylene recovered from commercial VI improver was compared as toheat stability with the tacky polymer products of this invention. Thecommercial polyisobutylene used in the following tests is made bypolymerizing isobutylene with boron fluoride-type catalysts. Its meanmolecular weight is indicated to be of the order 4,000 to 10,000 by themanufacturer.

The polyisobutylene was recovered from commercial Feed PolymerizationTests Polymer Analysts Physical Condition Mol Percent Propylene Conv.,Hrs. MIBK of Used Percent Wt. Percent Insoluble Catalyst Propylene 850F. at 200 F.

4 95 88 54 28 16 19 5. 8 Good. 7 95 92 72 52 44 16 7. 3 Good. 12.5 94 8659 40 24 14 6.2 Spalled Vl improver by the following procedure: The Vlimprover was completely dissolved in methylisobutylketone by heating toabout 230 F. Upon cooling the solution to room temperature, thepolyisobutylene precipitated out. The process was repeated on thepolyisobutylene twice more. The polyisobutylene did not completelydissolve in the MIBK the last two times. The crude polyisobutylene thusobtained was washed with methyl alcohol, and was then dissolved inchloroform. The polyisobutylene was precipitated from the chloroformsolution by the addition of methyl aicohol. The liquid was decanted,

and the purified polyisobutylene was dried. Drying was accomplished intwo ways, by heating in a vacuum oven at 212 F. for 8 hour-.sandbystorage in a vacuum dessicator at room temperaturefor several days.

' Thedat'a presentedinFigure4*were obtained byplacing a sample of thepolymer to be tested ina 'bomb and heating slowly. Pressure andtemperature were measured at intervals. Thepolyrners were all maintainedat each temperature -`for comparable times before the pressure was read.

The :data in Figure 5 were obtained by placing a sample ofthe poly-merYinn-av bomb and heating as rapidly as possible to the indicatedtemperature. Thettemperaturezwas then maintained constant,and'thepressure was `readrat intervals.

Figure fcompares'the stabilities of 'long-chain letin polymersrpreparedinac'cordance with the invention .over chromium oxide-silica-aluminacatalyst with that -of vthe polyisobutylene recovered from commercial VIimprover. It will be seen from the figure that the commercialpolyisobutylene is considerably less stable than are thepolymers of thisinvention. Whereas the former began tor'decompose at about 600 F., thelatter (polymers of propylene, I-butene, l-pentene, 1hexene, and4-methyl-1- pentene) began to decompose at about 700 to 725 F. A 1:1copolymer of 1-hexene and 4-methyl-1fpentene, prepared over chromiumoxide-silica-alumina catalyst, exhibited about the same stability as thepolymer of 4- methyl-l-pentene.

A 1;1.copolymer=of l-butene'andipropylene and the fiber-like polymer ofprOpylene, .bothprepared overl chromium oxide-silica-alumina catalyst,exhibited stabilities about equal to those ofthe vpolymers of l-buteneand propylene (tackynpolymer), respectively.

Figure 5 presents .data obtained in tests designed to determine moreexactly the decomposition temperatures of the commercial polyisobutyleneand of the polypropylene :ofthe subject invention. Upon interpolation ofthe data, lthe decomposition v temperatures of polypropylene and ofpolyisobutylene are seen to 'be about 700 F. and 590 F., respectively.Examination of the figure also indicates that at equal-'rates ofdecomposition, the temperature of the polypropylene is some 110 to 125F. higher than that for polyisobutylene.

Analysis of the gaseous products indicates that commercialpolyisobutylenedecomposes predominantly into isobutylenef(70.percent ofthe gaseous products). The polymers .produced over chromiumoxide-silica-alumina catalyst showed no markedtendencyto depolymerizeinto the originalolein monomer; in nocase was the yield of the originalmonomer greater than .31 percentof the gaseous products.

.Example X VII .TABLE .XVIII Wt. Percent SUS at VI Polymer 210 F.

'Data forblends of' high temperature lr-hexene'polymer v in SAE 20v`nished4 lubricating oil stoel: are. shown 24 in .Table XIX..and.in.Figure- 6 .as curve III; :Thegpolymer.was.prepared..at215Vover.chromium..oxide-silicaaluminaatalyst havingthe same compositionand prepare'dl by .thesame method as. that used. atV 170'* .F. -Thepolymer was concentrated. .by extraction with'methylethylketone.vTheploymer .was .dissolved .completely in atiSO Y C. '.Upon. coolingtovroomV temperature, aninsolublephase, whichfafmounted'to 47.5weight;,percent.of the original polymer, was recoveredlby-decantation..The insoluble material was again treated with MEK at 'C., partialsolution being obtainedfafter which the mixture was cooled to room:temperature -ariddecanted '.The remajningtpolymer (Iusedras `VIimproved) earnounted i to 3252 v'weight tpercentfcif :the'riginalpolymer. The foil recovered? from the trst MBK solutionizhasaVI of 31'22.and a .'iscosityv-atZlW-F. of 130.5- SUS.

T.ABLEcXIX .wtsrernt' .sus at f vr Polymer 1210o F. t

0 154.0 96 1 '-57.5 101 2 en -3 105 5 70.6 112 1o 95.9 119 1:15 1:65.141.109

' l Originalpolym'er-'noMEK'extraction.

Data "for commercial polyisbutylene are'presentedV in Table XXand in'Figure 6. These data, with the exception of one point, weretaken-'ironia generalized-curve supplied `byfthe manufacturer."Viscosity and of Ythe base oil are f taken into -iaccount 'by the fgraph. These data i indicate ha '.'grea-ter 'viscosity increase jfor thejpolyisobutylenef than for' either 2 l-hexene polymer. "The singleexperimental point-indicatesvlaboutthe same-viscosity increase forthe*polyisobutylenef-asfforfthe fhightempera- 1 Experlmentallydeterrninediorv SA-E 20 011. containing-f9.5 weight percent commercialp'olyisobutylene.

A11 indication of the greater stability'f blends of 'lubri- "cating `oil'with"tacl y polymer over'those with commercial polyisobutylene l isfound is the aluminum 'fblock test data presented in Table XXI. "The`base -ol was SAE 20 finished stock 'having a VI of96.

TABLE XXI Wt. 98 wt. Percent Percent Base Oil, Base Oil, Base Oil 5 wt.2 wt.

Percent Percent; Polyiso- Propylene butylene Polymer Solution 1 SamplelNo 7 9 10 SUS at. F., new "345. 6 493.1 546.1 SUQ at 100 F., blocksample-.-" 369.9 506: 4 '-557.6 Percent. Increase-. 7.0 .12.' 7 1Percent N aphtha Insoluble 0.12 0. 04 0. 02

rto25'-percem: active' ingredient.

asesinar Example XVIII A sample of polypropylene, prepared by thepolymerization of propylene over a chromium oxide-silica-aluminacatalyst, was fractionated by molecular distillation and the specificgravity and viscosity index were determined on each fraction. The dataare presented in Table XXII.

The 2-hexene, 3hexene, and 2methyl-2pentene cut s subject toisomerization conditions in a separate unit to produce l-hexene which isseparated as the lower boiling fraction. Isomerization of some of theZ-methyl-Z-pentene to 4-methyl-l-pentene and 4-methyl-2-pentene is alsoeffected and this fraction is removed as the low boiling cut and sent tothe first isomerization separation unit. Figure TABLE XXII Viscosity Wt.Cum. Sp. Gr. Cut Percent Wt. SUS Centistokes V. I 60/60 Percent F 100 F210 F. 100 F. 210 F 1 Wt. percent bottoms determined by derence. Thetraps contained 2.7 wt. percent ofthe charge.

2 Too viscous to measure.

It will be noted that the VI of the overhead fractions varied from 27 to76 While the charge had a VI of 102. This apparent discrepancy isprobably due to the VI-improving nature of the bottoms.

Example XIX Another modication of the invention is a combination processcomprising the steps of polymerizing propylene over nickeloxide-siliea-alumina catalyst to produce a dimer containing4-methyl-l-pentene, 4-methyl-2-pentene, 2-methyl-2-pentene and l, 2-,and 3-hexenes; fractionating this mixture to produce fractions of (l)4-methyl-lpentene, (2) 4methyl2pentene, (3) l-hexene and (4) 2- and3hexenes; isomerizing separately the 4-rnethyl-2- pentene and the 2- andB-hexenes to the l-isomers; combining these l-isomers with l-isomersoriginally produced, and polymerizing separately or co-polymerizingthese 1- isomers (l-hexene and 4-methyl-l-pentene) over chromiumoxide-alumina-silica catalyst. The l-hexene polymer is a tackytransparent gel suitable for a viscosity-index improver. The4-methyl-l-'pentene polymer is a tough solid polymer suitable for asubstitute for natural waxes. The propylene dimer is produced by thepolymerization of propylene over nickel oxide-silica-alumina catalyst inaccordance with U. S. Patent 2,606,940. The composition of the dimer ispresented in Table XXIII.

TABLE XXIII Dlmer Volume B. P., F.

Percent 4-methyl1pentenc 4 129 4methyl-2-pentene 51 1382-methyl-2-pentene 11 153 2-hexene and 3-hexene 33 152-1 54 Lheens 1 1453 shows the process steps in diagrammatic form and is self-explanatory.

In the isomerization steps, undesired hexenes which form are removed toprevent excess build-up. Isomerization catalysts, such as brucite andbaum'te, are useful.

The polymer produced from alpha-olefins over a chro miumoxide-containing catalyst has a wide molecular weight range. The totalpolymer can be separated into three fractions, a liquid fraction, atacky fraction, and a solid fraction containing material at the upperend of the molecular weight range. The separation may be carried out bya number of different methods, and the relative amount and thecharacteristics of the various fractions will depend somewhat on themethod of fractionation used. Two methods of separation are currentlyused: (l) The total polymer is fractionated under vacuum to produce anoverhead fraction having an end point, corrected to atmosphericpressure, of 850 to 900 F. The kettle material is then extracted withMIBK at a temperature somewhat above room temperature yielding asextract the tacky polymer and as ranate the solid polymer. (2) The totalpolymer is subjected to extraction with pentane at room temperature, thesolid fraction being insoluble. The pentane-soluble material is thenextracted, usually twice, with MIBK at room temperature yielding anextract of normally liquid oil and a rainate of tacky polymer. Method(l) produces considerably less oil and more tacky polymer than method(2). The oil produced by method (2) probably contains in solution someof the lower molecular weight tacky polymer. However, in the case ofethylene polymerization, only very small amounts of nonsolid polymer areproduced.

Example XX The material (propylene polymer) tested as a lube oilblending stock was prepared by method (2). The MIBK- soluble materialcomprised about 61.4 weight percent of the total polymer, and was testedas a lube oil blending stock without further treatment. This material,which has a viscosity of 1335 SUS at 210 F., was blended with a solventreiined Mid-Continent oil (39 SUS at 210 F.) in amounts of l0 and 18percent propylene polymer which yielded SAE 20 and 30 blends,respectively. The SAE l0 stock and the two blends were tested by meansof the well-known aluminum block test. In addition, the viscosity indexof each was determined. The results are presented in Table XXIV.

aasmar 'TABLE-XXIV t SAE 1o "sani zo SAE lso (Original v Blend .BlendOil) Sample No 8 11 12 V'I 99 120 122 Vis., New, SUS at 100 F 123. 7242.4 402. 0 Vis., block sample, SUS at 100 F- 130. 7 245.6 415.4Percent Vis. Increase 5. 1 1. 3 3. 3 Percent N aphtha Insoluble l 0.160. 02 0. 02 Neut. No 0.33 0.05 0. 05

1A slight granular deposit in Sample S after 24 hours in the blockindicates that the value shown for the napbthalnsoluble ls probably low.

branched vinyl typellof unsaturation.

" ples tested and also in allof the other. polymers made inaccordancewith our invention wastound to be trans-in- IISv Examinationof the above data indicates that the addition of the propylene polymeroil'to the .base stock not only increased the VI markedly, but alsoimparted increased resistance to oxidation, asshown by thelower valuesfor viscosity increase, naphtha insolubles, and neutralization number.

The weight average molecular weight of this tackypropylene polymer liesin the range of 500 to 5,000. The, solid polymer fraction is insolublein pentaue at room 4 temperature. The solid material has a melting pointin the range of 240 to 300 F., a density in the range of 0.90 to 0.95,an Iintrinsic viscosity in the range of 0.2 to .1.0, and a weightaverage molecular weight inthe range of approximately 5,000 to 120,000.Y

vThe poly'ethylene of the invention'is principallya solid polymerhavinga freezingA point in the range of .240.to 260 F., a density in therangeof 0.92 to 0.99, ordinarily 0.95 to 0.97, an intrinsic viscosity inthe rangeof 0.2.to 1:0, and a weight average molecular weight in theapproximate range of '5,000 to 250,000. The melting pointiis determinedfrom acooling curve of temperature vs. time; actually, this is afreezing point, though generally termed melting point in the art.

The molecular 'weights mentioned herein are weight average molecularweights and were calculated according to' the equation wherein M 'istheweight "average yrnolecular'wei'ght and Nl'isthe inherent viscosityas "determined for a solution of 012 gram of the-'polymer in 50 cc. oftetralinat 130 C. This type of molecular weight determination isdescribed by'Kernpand'Peters,'Ind.fEng. Chem. 35, 1108 (1943) aud-by`Dienes'an`d"Klemm, J. Applied Phys., 17, '458 (June 1946).

'A study and"comparison"was madebetween the 4polyethylene Yof theinvention and nine commercial `trademarked polyethylenes V'prepared 'byVhigh-pressure (e. g. 1`000100,000 p.'s. i.-)'polymerization.yItwas'foundV that the'polyethylene of ltheinvention'diiers materiallyin meltingY point from 'connnercialepolyethylenea its 'melting pointbeing in the range. of 240 to.260 F. Other polyethylenes hadconsiderably lower melting points, the closest one melting at about-228F. The .densityofour polyethylene' is also. higher thanthe ydensity ofother polyethylenes, the average density of several samples of ourpolyethylene produced in the'xed-bed modiiication of our processbeing0.952 as compared with 0.936 for the highest density of any ofthesecommercial polyethylenes tested. Another ysignificant diierence,betweenour polyethylene and lthe commercial lpolyethylenes is in theShore D hardness which isfromi60 to,75^for our polyethylene as comparedwith 48`forfthehardestof thecommercial polyethylenes here tested.

'The reason 'for the higher melting point, greaterdensity, and hardnessof our polyethylenefas ycompared with the commercial polyethylenesappears to be due to the difternal and/ or terminal vinyl.Trans-internal type of unsaturation is represented by therforrnula Thevte1'mi11a1'-r'rinyl type'of unsaturations-is characterized by thestructure -CH=CH2. The'vinylgroupmaybe Iattached f to fthe rmoleculeeither linternally or .terminally as represented, for example, by suchformulas as:

CII

(terminal vinyl) The characteristic of branched vinyl type ofuusaturation is two'hydroca'rbon radical substituents attached to 'the'same carbonatom of the viny group'and two hydrogen atoms -attached tothe yother carbon atomof the vinyl group. rangement of the majorVportionof the .unsaturation in all of our polymers studiedby-infra'red; spectroscopyis` probably due to the mechanism.of our novelYpolymerizationY reactionin .the presence...of chromium. oxide catalystwhich -isdifterent-,fromlthat futilizedflinathe, polymerizationreactions ofthe priorl art. .L'I`-he.same type of =unsaturationis found.in -allof our polymers, including copolymers suchas.ethylene-propylene` copolymers. Ittislprobably dueto the mechanism44by` which the olefin v 'units fare builtinto largelmoleculeswhichaccounts for the ..position of Athe unsaturation: of .the moleculeeandalso accounts forn the differentVv characteristics .of-.the resultingpolymer.

A. .comparison of. the .type .oft .unsaturatiomt in V.double bonds ,per1000 carbon atatoms, possessed .by -;our vpoly-r ethylene, produced. inaa iixedabed .process with that .of two representative.commercialpolyethyleues is shown in-fllable.

XXV.

The trans-internal and/or terminal vinyl `.ar-

1. A PROCESS WHICH COMPRISING POLYMERIZING AT LEAST ONE POLYMERIZABLEOLEFIN, AT A POLYMERIZATION TEMPERATURE UP TO ABOUT 500*F., WITH ACATALYST ACTIVE FOR SUCH POLYMERIZATION AND COMPRISING, AS THE SOLEESSENTIAL EFFECTTIVE CATALYTIC INGREDIENTS THEREOF, CHROMIUM OXIDE ANDAT LEAST ONE MATERIAL SELECTED FORM THE GROUP CONSISTING OF SILICA,ALUMINA, ZICRONIA, AND THORIA, AT LEAST PART OF THE CHROMIUM BEING INTHE HEXAVALENT STATE AT THE INITIAL CONTACTING OF HYDROCARBON WITH SAIDCATALYST.